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IntroductionEnergy Engineering and Environmental Protection Publications
Espoo 2001 TKK-ENY-7
(apurahoitus) 2001 Antti Tohka, Ron Zevenhoven
Helsinki University of Technology
Department of Mechanical Engineering
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Preface
Brominated flame retardants (BFRs) are widely used, often together with antimony-based
flame retardants, in electronic and electric equipment, furniture and office equipment. While
this increases the fire safety for these products, the BFRs are problematic when thermal
processes are used during the treatment of waste streams from these products, such as waste
from electrical and electronic equipment (WEEE). Not only do the BFRs negatively effect the
incineration of old furniture, they interfere with thermal processes that aim at the recovery of,
for example, valuable metals from WEEE.
This report gives an overview of which and how much BFRs are found in various products
and waste streams and what problems this may bring to thermal processes for recovery and
recycling or during incineration or waste-to-energy processing. Also the formation of
brominated analogues of dioxins and furans, PBDD/Fs (poly brominated dibenzo -p- dioxins
and - furans) is addressed, and analytical methods that allow for the identification and
measurement of concentrations of brominated chemicals during thermal processing of BFR-
containing waste streams. What is not given in this report is a discussion on different waste treatment methods and how
all these are affected by BFRs. Also, the issue of bromine-related corrosion is mentioned but
could not be analysed in depth due to a lack of relevant literature. The same holds for the
consequences of methyl bromide (or bromoform, CH3Br) being an ozone depleting substance.
Instead, this study aimed at summarising the reasons for, and consequences of the presence of
BFR compounds in waste streams, while taking into consideration the options for recovery of
bromine. This study was funded by Ekokem Oy Ab support funding (apurahoitus) 2001.
Espoo, April 2002
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List of contents 1. Introduction 7 2. The Chemistry of Brominated Flame Retardants 8
2.1 Types of flame retardants 8 2.2 Mechanisms of action 9 2.3 Synergism, antimony oxide 12 2.4 Chemical properties of bromide 12
3. The Properties of Brominated Flame Retardants 13
3.1 Tetrabromo bisphenol A (TBBPA) 13 3.2 Polybrominated diphenyl ethers (PBDEs) 15 3.3 Polybrominated biphenyls (PBBs) 17 3.4 Hexabromo cyclododecane (HBCD) 18 3.5 Other BFRs 18
4. BFRs in Consumer Products and E+E Equipment 19
4.1 BFRs in textiles 19 4.2 BFRs in E+E equipment 21 4.2.1 Printed circuit boards 21 4.2.2 Housing of E+E equipment 23 4.3 Building materials 26 4.4 Other applications of BFRs: paint, transportation 26
5. BFR-containing Products and Waste Streams 28
5.1 Finland 28 5.2 Sweden 29 5.3 Denmark 29 5.4 EU 32 5.5 USA 32 5.6 Japan 32 5.7 BFR markets world wide 33
6. Legislation 35 7. Treatment of Wastes Containing Brominated Flame Retardants 38 7.1 Mechanical recycling (of waste streams such as WEEE) 38 7.2 Thermal treatment of bromine-containing wastes: general aspects 39 7.2.1 Contamination by BFRs and recovery / recycling 39
7.2.2 Recovery of bromine from bromine-containg wastes 40
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7.3 Thermal treatment of bromine-containing waste: processes 42 7.3.1 Rotary kiln furnaces 43 7.3.2 Mass burning on a grate 43 7.3.3 Fluidised bed reactors 44 7.3.4 Pyrolysis drums and other pyrolysis systems 45 7.4 Formation of brominated dioxins and furans during thermal
processing of BFR-containing wastes 46 8. On-line and Off-line Analysis Techniques for Identification
and Concentration Measurement of Brominated Chemicals in Waste Streams and Gases 49 8.1 Mass spectroscopy 49 8.2 Infrared (IR) spectroscopy 51 8.3 Other methods 52
9. Summarising Conclusions 53 10. References 55
List of Abbreviations
Brominated flame retardants (BFRs) are widely used, often together with antimony-based
flame retardants, in electronic and electric equipment, furniture and office equipment. While
this increases the fire safety for these products, the BFRs are problematic when thermal
processes are used during the treatment of waste streams from these products, such as waste
from electrical and electronic equipment (WEEE). Not only do the BFRs negatively effect the
incineration of old furniture, they interfere with thermal processes that aim at the recovery of,
for example, valuable metals from WEEE.
A flame retardant should inhibit or suppress a combustion process and that's why they are
used in products which would otherwise have a high risk of fire. Including flame retardant
into products is one way to improve their fire safety relatively cheap way. Depending on their
nature, flame retardants can act chemically and/or physically in solid, liquid or gas phase.
They interfere with combustion during a particular stage of this process, e.g. during heating,
decomposition, ignition or flame spread [1]. For BFRs the high molecular weight provides
numerous advantages from manifacturers point of view are such as low volatility, low
migration rates at surface, ease of handling.
This report gives an overview of which and how much BFRs are found in various products
and waste streams and what problems this may bring to thermal processes for recovery and
recycling or during incineration or waste-to-energy processing. Also the formation of
brominated analogues of dioxins and furans, PBDD/Fs (poly brominated dibenzo -p- dioxins
and - furans) is addressed, and analytical methods that allow for the identification and
measurement of concentrations of brominated chemicals during thermal processing of BFR-
containing waste streams.
Bromine-related corrosion and the ozone depleting properties of methyl bromide (bromoform)
are mentioned but not discussed.
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2.1 Types of flame retardants
Flame retardants are added to polymeric materials, both natural and synthetic, to enhance the
flame-retardancy properties of the polymers.
There are four main groups of flame retardant chemicals:
- Inorganic flame retardants including aluminium trioxide, magnesium hydroxide,
ammonium polyphosphate and red phosphorous.
- Halogenated flame retardants, primarily based on chlorine and bromine. The brominated
flame retardants are included in this group.
- Organophosphorous flame retardants are primarily phosphate esters. Organophosphorous
flame retardants may contain bromine or chloride.
- Nitrogen-based organic flame retardants are used for a limited number of polymers.
2.2 Mechanisms of action
Depending on their type, flame retardants can act chemically and/or physically in the solid,
liquid or gas phase. They interfere with combustion during a particular stage of this process,
e.g. during heating, decomposition, ignition or flame spread. Substitution of one type of flame
retardants by another means a change in the mechanisms of flame retardancy.
Halogen containing flame retardants act primarily by a chemical interference with the radical
chain mechanism taking place in the gas phase during combustion. High-energy OH and H
radicals formed during combustion are removed by bromine released from the flame retardant
as described in reactions 1-7. The basic concept is given in Figure 1.
H + O2 → OH + O (1)
O + H2 → OH + H (2)
The halogen retardant RX initially breaks down:
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RX → R + X (3)
where X is either Cl or Br. The halogen radical reacts to form the hydrogen halide as
described in reaction 4:
X + RH → R + HX (4)
which in turn interferes with the radical chain mechanism shown in reactions 5 and 6:
HX + H → H2 + X (5)
HX + OH → H2O + X (6)
The high energy H and OH radicals are removed by reactions with HX and replaced with low
energy X radicals. The actual retardant effect is thus produced by HX. The hydrogen halide
consumed is regenerated by reaction with hydrocarbon as in reaction 7:
X + RH → R + HX (7)
Thus HX ultimately acts as a (negative) catalyst. The radical interception mechanism is
questioned by E.R. Larsen (for example in Fire & Flammability 10, 1979) who surmises that
physical mechanism lies behind the flame retardant effect of halogen compounds. After all,
hydrogen halides are non-flammable gases but also form non-combustible protective layers
interfering with or halting the combustion process. [1]
Several authors have pointed out that halogen containing flame retardants are also effective in
the condensed phase. [1]
10
Figure 1 BFR acting principles: interruption of the radical chain mechanism of the combustion process in the gas phase. (picture taken from [2])
Although brominated flame retardants are a highly diverse group of compounds the flame-
retardancy mechanism is basically the same for all compounds. However, there are
differences in flame-retardancy performance of the brominated compounds, as the presence of
these compounds in a polymer will influence the physical properties of the polymer.
In general aliphatic bromine compounds are easier to break down and hence more effective at
lower temperatures, but also less temperature resistant than aromatic retardants. [1]
Aluminium hydroxide and other hydroxides act in a combination of various processes. When
heated the hydroxides release water vapour that cool the substrate to a temperature below that
required for sustaining of the combustion processes. The water vapour liberated has also a
diluting effect on the gas phase and forms an oxygen-displacing protective layer. Additionally
the oxide (e.g. AlO2) forms, together with the charring products, an insulating protective
layer.
Phosphorous compounds mainly influence the reactions taking place in the solid phase. By
thermal decomposition the flame retardant is converted to phosphorous acid, which extracts
water from the pyrolysing substrate, causing it to char. However, some phosphorous
compounds may, similar to halogens, act in the gas phase as well by a radical trap
mechanism.
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Nitrogen-based flame retardants like melamine and melamine derivatives act by
intumescence. These flame retardants are most often used in combination with other flame
retardants. Gases released from the compounds make the material swell and form a insulating
char on the surface.
A distinction is made between reactive and additive flame retardants. Reactive flame
retardants are built chemically into the polymer molecule, together with the other starting
components. This prevents them from bleeding out of the polymer and vaporise and their
flame retardancy is thus retained. They have no plasticising effect and do not affect the
thermal stability of the polymer. They are used mainly in thermosets, especially polyesters,
epoxy resins and polyurethanes (PUR) in which they can be easily incorporated.
The most widely used reactive brominated flame retardants are tetrabromobisphenol A
(TBBPA), tetrabromophthalic anhydride, dibromoneopentylglycol, and brominated styrene.
Additive flame retardants are incorporated in the plastic either prior to, during, or, more
frequently, following polymerisation. They are used especially in thermoplastics such as
ABS, HIPS, PS, PC and thermoplastic polyesters. If they are compatible with the plastic they
act as plasticisers, otherwise they are considered to be fillers. They are sometimes volatile and
tend to bleed, so their flame retardancy may be gradually lost. High molecular weight
products are developed to enable plastics to be made more permanently fire retardant by the
additive method.
The most used additive brominated flame retardants are polybrominated diphenyl ethers
(PBDEs), tetrabromobisphenol A (mostly used as reactive FR) and hexabromocyclododecane
(HBCD).
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2.3 Synergism, antimony oxide
Combinations of flame retardants can produce an additive or a synergistic effect. While the
additive effect is the sum of the individual actions, the effects of synergism are higher than
this sum.
Antimony trioxide, Sb2O3, the main antimony compound used commercially, shows no
perceptible flame-retardant action on its own. Together with bromine-containing compounds,
however, it produces a marked synergistic effect. Antimony trioxide is widely used in
brominated FR formulations.
2.4 Chemical properties of bromine
Bromine has two stable isotopes (mass number 79 and 81) present in the earth’s surface layer
for 50.5% as 79Br and 49.5% as 81Br. There are 35 electrons in the electron shells, 35 protons
in the nucleus, and 44 and 46 neutrons, respectively in the nuclei of the two stable isotopes.
Both isotopes have nuclear spins of 3/2 and exhibit quadrupole moments. The electronic
configuration in the valence shell is 4s24p2, lacking one from having the inert gas
configuration. Bromine has a strong affinity for a complete the outer shell, but somewhat
weaker than for chlorine. This is because the nuclear attraction for the valence electrons is
more screened in bromine than in chlorine. The effect of this may be seen from the values for
ionization potentials, and the dissociation constant of Br2 and Cl2 at a given temperature. [3]
Bromine adds to double and triple bonds and it participates similar to chlorine in substitution
reactions. The principal differences to chlorine are attributed to the larger size of the bromine
atom with its larger number of electrons screening the attraction of the nucleus on valence
shell electrons. Thus, despite the oxidising power of bromine the formation of some fully
brominated structures is difficult. [3]
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3. The Properties of Brominated Flame Retardants
A BFR may be defined as “a non-organo phosphoros organic compound where one or more
hydrogen atoms are replaced by bromine” [4]. This definition excludes ammonium bromide
and brominated organophosphates. BFRs contain 50-95 %-wt bromine, and can be separated
into aromatic, aliphatic and cyclo-aliphatic. There are over 40 different BFR types in
commercial use but basically only a handful of those are used on a large scale.
The aromatic BFRS can be divided into three types, i.e. polybrominated diphenyl ethers
(PBDEs), tetrabromo bisphenol A (TBBPA) and its derivates, and polybrominated biphenyls
(PBBs). Of the cycloaliphatic BFRs compounds, hexabromocyclododecane (HBCD) is the
most important. Aliphatic BFRs are not used in large amounts since they are less stable than
aromatic BFRs; they may be more effective at lower temperatures, however. Each of these
BFRs has very different properties and that why it’s important to know which kind of BFR is
discussed. Different types of BFRs should never be assimilated when referred to, especially
when it comes to toxicological issues.
3.1 Tetrabromobisphenol A
The most widely used BFR compound nowadays is tetrabromobisphenol A, TBBPA. Its trade
name is FR-1524. TBBPAs and their derivatives such as TBBPA bis-(2-hydroxyethylether)
are a group of aromatic BFRs in which four hydrogens in the bisphenol structure are replaced
by bromine (see Figure 2). Their market share is currently over 50% world wide.
Br
BrBr
OH
Br
HO
CH3
C
CH3
MW: 543.7 g/mol
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TBBPA’s and derivatives’ main use were as reactive FR for unsaturated polyester (UPE) and
as additive FR for polybutylene terepthalate (PBT), polyethylene terephtalatete (PET) and
ABS plastics [4]. Some of the major applications for TBBPA have been in printed circuit
board laminates, housings of electric or electronic equipment such as PC monitors and in
transportation applications such as a car’s plastic parts.
Typical properties of TBBPA are listed in Table 1.
Table 1 Properties of TBBPA. [5]
Appearance White crystalline powder
Bromides ppm 75
Results from a thermogravimetric analysis (heat up 10 °C/minute, in air), are presented in
Table 2.
Weight loss % Temperature °C
3.2 Polybrominated diphenyl ethers (PBDEs)
Polybrominated diphenyl ethers are the most interesting and the most discussed BFRs because
of their wide use in electric and electronic appliances. PBDEs are a group of aromatic
brominated compounds in which one to ten hydrogens in a diphenyl oxide structure are
replaced by bromine. PBDEs have a large number of congeners, depending on the number or
position of bromine atoms on the two phenyl rings. The total number of possible congeners is
209, and numbers of isomers for mono-, di-, tri-, up to decabromo diphenyl ethers are: 3, 12,
24, 42, 26, 42, 24, 12, 3 and 1. Technical PDBE products are produced by brominating
diphenyl ether in the presence of a catalyst. [6]
PBDEs can be divided into two different groups according their bromine content: lower such
as Tetra-BDE, Penta-BDE and Hexa-BDE or a higher content such as Hepta-, Nona-BDE,
Deca-BDE and Octa-BDE, of which Deca-BDE (see Figure 3) is according to the Bromine
Science and Environmental Forum the most common compound (see Table 14). According to
laboratory experiments made by Watanabe and Tatsukawa in 1987, Deca-BDE has been
shown to photolytically degrate and form lower brominated PBDE. [6]
Major uses for PBDEs are plastic housings of smaller office equipment etc. (which are
usually made of high impact polystyrene HIPS plastic) and in PE plastics. Nowadays
PBDEs’ market share is declining while manufacturers are switching their flame retardants to
non-halogen ones. The main reason for this trend has been environmental concern about
PBDEs toxicological effects [6] and (up)coming regulation changes especially in Europe [7].
O
Br
Br
BrBr
BrBr
BrBr
Br
Br
MW: 959.2 g/mol
Figure 3. FR-1210 Decabromodiphenyl ether (DeBDE). (picture taken from [4])
Typical properties of DeBDE are listed in Table 3.
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Appearance Free flowing micronized,
white to off-white powder
Results from a thermogravimetric analysis of De-BDE (heat-up10 °C/minute, in air), are presented in Table 4.
Table 4. Thermogravimetric analysis on DeBDE. [4,5]
Weight loss % Temperature °C
1 319.5-322
5 353.10-362
10 370.5-385
50 414
90 436
Printed circuit boards typically do not contain any of the three commercial PBDEs. [8] In the
literature it is mentioned that Asian types of phenolic paper/laminate could contain PBDE. [9]
The commercial PBDE are produced by the bromination of diphenyl oxide under certain
conditions, which results in products containing mixtures of brominated diphenyl ethers. The
commercial PBDEs are rather stable compounds with boiling points ranging between 310
and 425 ºC and low vapour pressures, e.g., 3.85-13.3 Pa at 20-25 ºC; they are lipophilic
substances. Their solubility to water is very poor, especially that of the higher brominated
diphenyl ethers, and the n-octanol/water partition coefficients range between 4.28 and 9.9.
Polybrominated diphenyl ethers have not been reported to occur naturally in the environment,
but other types of BDE have been found in marine organisms. [6]
Table 5 presents compositions of commercial brominated diphenyl ethers.
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Product Composition
DeBDE
3.3 Polybrominated biphenyls (PBBs)
Polybrominated biphenyls (PBBs) are a group of halogenated hydrocarbons which are formed
by substituting bromine for hydrogen in biphenyl (see Figure 4). According to the OECD,
decabromobiphenyl (DeBB) is the only brominated biphenyl that has been identified in
commercial use. DeBB has tradionally been used as additive flame retardant for styrenic
polymers and engineering plastics [4]. PBBs can be found in TV and computer housings and
textiles.
Figure 4. Decabromobiphenyl (DeBB). (picture taken from [4])
Nowadays the production of PBBs has been phased out [8] but it’ll take years before all PBB-
containing items have reached the end of their life cycle and waste management doesn’t have
to concider of these compounds anymore.
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Hexabromocylododecane (HBCD) is a cycloaliphatic compound with six bromine atoms (see
Figure 5). HBCD is produced by bromation of cyclododecane in a batch process. HBCD has
been used for about 20 years [10]. Major users of HBCD are textile industry (coatings) and
building and construction industry (flame retarted insulation). End products containing HBCD
include upholstered furniture, building materials and interior textiles and cushions for
vehicles.
MW 641.4 g/mol
3.5 Other BFRs
The above mentioned brominated flame retardants represented about 76% of the 1992 global
production of BFRs. [4] The remaining is covered by a number of other retardants. The most
of them are presented briefly in Table 6.
Table 6 Other BFRs and their use. [4]
Chemical Bromine content (%) Reactive Additive Main applications (globally) TBPA diester/ether diol 45 + rigid PUR foams
Ethylene bis(tetrabromophthalimide) (EBTBP) 67 + similar to DeBDE Tetrabromophthalimide 69 + engin. thermoplast.
Disodium salt of tetrabromophthalate 15 + textile, coatings Dibromoethyldibromocyclohexane 75 + PS, PUR
Ethylene bis(dibromonorbornanedicarboximide) 48 + nylons and polyolefins Dibromoneopentyl glycol (DBNPG) 61 + UPE, PUR
Tribromoneopentyl alcohol (TBNPA) 72 + PUR Vinyl bromide (VBr) 75 + modacrylic fibers
2,4,6-Tribromophenol (TBP) 73 + phenolics, epoxy Bis(tribromophenoxy)ethane (HBPE) 70 + ABS, PC, thermosets
Poly(dibromophenylene oxide) (PDBPO) 62 + similar to DeBDE Pentabromoethylbenzene (5BEB) 82 + UPE, SBR, textile
Poly(pentabromobenzyl acrylate) (PBB-PA) 70 + polymeric, PBT Polydibromostyrene (PDBS) 59 + PA, PBT, styrenics
Brominated polystyrene (BrPS) 60 + PBT, PS
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4.1 BFRs in Textiles
Brominated flame retardants can be found in the following textiles: upholstered furniture,
clothing, particularly protective clothing, carpets, curtains, tents, vehicle interiors (excluding
airplanes), offices, public and larger premises, glass fibre products and other technical
textiles. [4]
Flames from cigarettes, candles or matches are typical reason for residental fire deaths. Flame
retard chemicals can be incorporated within fibres, applied to the surface of the textile, or
applied to the back of the textile in the form of a polymeric coating. [11] It is estimated that
FR chemicals would be applied as formulations in as much as 600 square yards of upholstery
fabrics each year. [12]
Flame retardants must have an element of transferability from the back into the whole fabric
and therefore they are almost always based on so-called vapor-phase active antimony-bromine
(or other halogen). Products comprise brominated species such as DeBPE or HBCD and
Sb2O3. [12]
Antimony-halogen flame retardants are currently the most successful within the back-coated
textile areas when considering cost and effectiveness. Unlike the fibre reactive, durable
phosphorous- and nitrogen - containing flame retardants used in cellulosic fibres, they can
only be applied topically in a resin binder, usually as a back-coating. [12]
"The worst case scenario" numbers for total add-on of FR agent in fabrics are 25% for both
Sb-DBDPE and Sb-HBCD where the mass fraction for Br is 12% and for Sb 7% in both
cases. [12]
Table 7 lists durably-finished and inherent flame retardand fibres in common use.
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Table 7. Durably-finished and inherent flame retardand fibres in common use [12]
Fibre Flame Retardant Structural Components Mode of
Introduction*
Natural
or reactive species
A
comonomer, phosphorous containing additive
compounds
C
Polyhaloalkenes PVC, polyvinylidene chloride H
High heat and flame
terephthalamide)
Ar
* F = Chemical finish ; A = Additive introduce during fiber production; C = Copolymetric modifications;
H = Homopolymer; Ar = Aromatic homo- or copolymer
The expanded polystyrene stuffing in sack chairs, health mattresses, nursing cushions, etc., is
normally flame retarded with between 0.5% and 1% HBCD. [12] Worldwide, tents are one of
the major textile end-products for BFRs. They are used both military tents and civil tents,
especially "party" tents. [12] The used BFRs are most likely the same decabromo-diphenyl
oxide or hexabromocyclododecane and Sb2O3 as in the back-coated textile areas.
Industry information indicates that PBDEs or other BFRs might be present in flame retarded
carpets based on cheaper synthetic fibres, where they are encapsulated within the polymer
fibres. [12]
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Many large manufacturers have voluntarily chosen to abstain from the use of BFRs in their
furniture and textile range. For example IKEA’s policy is to use flame retardants only when
legislation makes this necessary and in those cases choose alternatives for BFRs.
4.2 BFRs in E+E equipment
Electric and electronic (E+E) equipment usually accounts for the best known and well-studied
consumption of BFRs. Typical targets of interest are printed circuit boards and housing of
electric and electronic products. Other sources for E+E BFRs are lighting, wirings and
housings of electronic appliances. A reason for this special interest can be noticed from
Figure 6 where a compilation of statistics on reasons for residental fires in Finland have been
presented.
Figure 6 A source of inflammation in residental fires in apartment houses in Finland. [13]
4.2.1 Printed Circuit Boards
Printed circuit boards are assemblies consisting of a copper-foiled laminate over a glass fibre
"heart" on which small electric and electronic components, encapsulated in plastic (more
common) and metal, are mounted. Both the laminates and the plastic for encapsulation are
flame retarded, usually with brominated flame retardans. [4]
There are 2 main groups of laminates, being flexible and non-flexible ones.
Residental fires in apartment house
22 %
15 %
The reinforced non-flexible laminates consist usually of either glass fibre reinforced epoxy
(FR 4), or cellulose paper reinforced phenolic resin (FR 2). FR4 is the most used laminate
nowadays and it usually contains 15% TBBPA. In industrial and office electronics, e.g.
computers and electronics for telecommunication, the circuit boards are generally based on
FR4 or similar type of laminate. The TBBPA content of the most used 1.6 mm FR4 laminate
can be estimated at 0.42 kg/m2. [4]
By the early 1990s FR2 laminates were flame retarded with TBBPA in Europe and with
PeBDE in Asia. For both types the content of a typical FR2 laminate has been estimated at
0.036 kg/m2. During recent years it seems there has been a shift away from PeBDE, and today
most Asian FR2 laminates seem to be retarded with TBBPA. As a rough estimate it is
assumed that PBDEs still cover 30% of the FR2 laminates in consumer electronics other than
TV-sets. [4]
Traditionally printed circuit boards for TV sets and home electronic appliances have been
based on FR2 , but within high-priced market segments there has been a trend towards circuit
boards based on FR4. It can however be assumed that FR2 is still the dominating laminate in
this area of E+E equipment.
Plastic encapsulation of electronic components on a circuit board is predominantly made of
epoxy resin with TBBPA. Of the top ten component groups by volume, seven groups contain
TBBPA. These groups are plastic/paper capacitors, microprocessors, bipolar power
transistors, IGBT power modules, ASICs, and metal oxide varistors. None of the top ten
groups contain other brominated flame retardants. [4]
The concentration of TBBPA in the plastic encapsulations is relatively low. The plastic
encapsulation of an integrated circuit (chip) is reported to contain approx. 20-30% epoxy with
approx. 2% TBBPA incorporated.
Various analyses of printed circuit board waste from the literature are presented in Table 8.
23
Taiwan, 1999 [14]
Europe, 2001 [15]
Europe, 2000 [16]
German report 1992 [17]
Carbon 52.21 42.5 53.7 19 Hydrogen 6.11 5.03 5.59 Oxygen Balance 22.01 Nitrogen 2.56 3.72 Bromine 8.53 4.97 1.85 4
Sulfur Trace 0.032 0.08 Chlorine Trace 0.023 2.3 Copper 9.53 4.21 7
Moisture 3.50 1.7
4.2.2 Housing of Electric and Electronic Equipment There are two basic reasons why TV- sets are one of the major sources of domestical fires.
TVs and monitors are usually quite hot because a cathode ray tube needs certain working
temperature and they are usually collecting significant amounts of dust through the ventilation
holes. This is the reason why housings of computer monitors and TV sets are major
applications for BFRs, mainly PDBEs. In the United States, Canada, Australia and Japan
there has been very strict legislation in order to make monitors and TVs more safe and in year
2002 new EU standards will be set for fire safety of TV sets. However, it won’t probably
increase the consumption of BFRs because the industry has moved towards bromine-free
flame retardants.
Housings or enclosures for computer monitors and other appliances are predominantly made
from high-impact polystyrene (HIPS), ABS-polycarbonate blends or ABS-based flame
retardant compounds, although polypropylene (PP), polycarbonate (PC) and blends of
polyphenylene ether (PPE) and styrene/butadiene polymer may be used as well. In the early
1990s, HIPS represented 30% of the global De-BDE consumption, and ABS accounted for
around 95% of the total Oc-BDE supplied in the EU. [4]
Back panels - and to some extent the front cabinet - of TV sets are usually made of flame
retarded materials. In the USA and Japan, BFRs are still used in back panels and the front
cabinet (USA) of TV sets, but in TV sets purchased in Europe the front cabinet does not
contain flame retardants, and there is a trend away from the use of halogenated additives in
back panels. Based on the monitoring of the German magazine Stiftung Warentest it has been
shown that the percentage of tested TV set enclosures that contained halogenated flame
24
retardants decreased from 68% in 1994 to 8% in 1997 as shown in Figure 7. It should be
noted that the different tests do not cover the same market segment; some of the test for
example only include 17'' TV sets. However, the trend seems to be clear. The absence of
BFRs in European TV sets and the possible effect on the flammability of the TV sets have
been discussed in media. [4]
Figure 7. Percentage of tested TV set enclosures containing halogenated flame retardants according to several journal articles. (picture taken from [4])
In year 2000 Finland’s Safety Technology Authority (TUKES) has tested twenty-one TVs and
one PC monitor type in flammability tests. They analysed for inorganic elements and
compounds with SEM+EDS analysers and with XRD, respectively. The results are presented
in Table 9.
On the basis of Table 9, probably only one Italian-made Phillips TV set has bromine-based
FR included in its housing. There are still many unidentified spectral peaks but non of them
are related to bromine compounds, because there isn’t any elemental bromine found.
The most of other consumer electronics - radios, videos, etc. - are considered not to contain
BFRs in the housing. [4] The housing of office machines - computers, printers, copying
machines, fax machines, etc. - is made of flame retarded plastic. PBDEs have traditionally
been used for flame retardancy, but during the last years TBBPA and non-halogen flame
retardants have been substituted for the PBDEs.
0
20
40
60
4/93 11/93 5/94 11/94 5/95 11/95 5/96 11/96 5/97 11/97
Date of publication
s
25
Table 9. Flammability tests with various TV sets made in Finland 2000. [18] Type Country of
manufacture inorganic elements
Schneider Euro 245 Nicam Germany calcium, barium, sulphate
baryta white (barium sulphate) BaSO4
Schneider Scenaro 215 SN Germany calcium not indentified Nokia SP 55 B1 Germany calcium
calcium carbonate
CaCO3 Salora MP 2 55 A2 UK calcium calcium carbonate
CaCO3 Salora 28 M 91 Nicam/PIP Finland - -
Finlux 5028 (u) 28 U 40 TX
Finland - -
Sanyo 28ER15N EB4-A28 UK - - Philips PZ1 20PT1553/11 Europe magnesium, silicon,
aluminum, calcium, titanium
Philips 20PT155B/13 S Italy antimony, bromine antimony oxide Sb2O3, (bromine compound,
not identified ) Sony KV C2983E Spain antimony,
phosphorous antimony oxide Sb2O3,
identified) Salora MP 51 A2 Germany barium, sulphurous barium sulfphate
BaSO4 Oceanic 7294 Cinescreen Finland magnesium, alumium,
silicon not identified peaks
Philips 28PT4323/11 France - - Sony KV 29X 5E Spain antimony, titanium,
chrome, phosphorous
Nokia 6355 Nicam ID Germany barium, sulphur barium sulphate BaSO4
Sony KV-25X1E UK antimony, titanium, chrome, phosphorous
Sony KV-25X5E Spain antimony, titanium, chrome, phosphorous
not identified peaks
Philips 28PT4473/11 SL6.2
Philips 28PT4323/11 SL6.2
magnesium, titanium, silicon, phosphorous
26
Test results of electronic products on the German market show that out of more than 150
computer monitors, notebooks (portable computers) and printers tested in 1997/98, none
contained PBDEs or PBBs (the source of information is confidential). Of the bromine
containing products 72% contained TBBPA. The remaining 28% contained other non-
identified BFRs. [4]
4.3 Building materials
There are basically three different applications for potential BFR source in building materials:
synthetic insulation materials, translucent and glass fibre reinforced panels and polyolefin
based foils. In insulation materials expanded polystyrene (EPS), extruded polystyrene foams
(XPS) and polyurethane foams (PUR foams) can contain BFRs.
EPS and XPS are at large used for comparable purposes. Still, XPS is more durable and more
expensive than EPS, and this does influence the actual application of the two materials. In
Europe, both materials are normally flame retarded with hexabromocyclododecane (HBCD).
In EPS between 0.5 wt-% and 1 wt-% is found, and in XPS between 1 wt-% and 2 wt-% is
found. [4]
PUR may be flame retarded with both additive and reactive brominated flame retardants. The
dominant flame retardants for polyurethanes are brominated polyols, which are reactive flame
retardants. If requirements are strict, other additives and reactives may be combined with the
brominated polyol. In a number of applications flame retardants, and hence also BFRs, are not
used. These are home-refrigerators and district heating pipes (some indoor uses e.g. in
factories may imply the use of BFRs).
4.4 Other applications of BFRs : paint, transportation
Paints can be flame retarded for fire protection of steel and wood constructions. Other types
are "Low flame spread" paints that have no protective effect, but are included also as not to
nourish and spread a fire. Table 10 lists the amounts and types of BFRs which are used in
paints, fillers and fire proofing panels in Denmark.
27
wood impregnation and fillers in Denmark 1997. [4]
Product group Total consumption of BFRs Consumption of specific compounds (tonnes)
Tonnes Trend PBDE TBBPA PBB HBCD Other BFRs
Paint 0.1-0.3 ? 0.1-0.3
Basically, industry uses non-brominated compounds in aplications such described in Table
10. These FR types include nitrogen and phosphorous flame retardants. Exception is PUR
based fillers which were presented in chapter dealing with building materials.
In the transportation sector (cars, trains, trucks – but not aeroplanes !) BFRs are used in foams
(PUR see chapter 4.3), electronic and electrical systems such as printed circuit boards (see
chapter 4.2.), cushions and interior textiles (see chapter 4.1).
BFRs can be also found in films, video tapes and packaging materials. Expanded polystyrene
(EPS) is widespread used as packaging for fragile equipment. EPS packaging for electronic
equipment may contain HBCD as flame retardant. [4] Uses for these purposies are very
limited comparing to others.
5. BFR- containing Products and Waste Streams
5.1 Finland There aren’t any detailed studies on BFR streams in products and wastes in Finland, although
some estimations and BFR flow analyses have been made in other Nordic countries (see
Chapters 5.2 and 5.3), which can be useful also in estimating BFR volumes in Finland. In
order to estimate BFR streams in Finland there are couple of methods available. Possible
methods could be using raports of TUKES (Finland’s Safety Authority), reporting several
flammability tests with electrical and electronic equipment [18, 19], and estimations from
trade statistics shown in Figure 8.
0
50000
100000
150000
200000
year
equipment in Year 1997 [tons ]: IT equipment 21 000
Small electrical equipment (brown
56 000
brown goods) 18 000
Figure 8 Electric and Electronic imports in Finland and market amounts of most of them (excluding household or enterteiment goods such as control and laboratory equipment). [20]
Basically according to TUKES FTIR measurements in [19] no HBr emissions were detected
in fire safety measurements of randomly chosen TV, refrigerator, dishwasher and washing
machines. HCl was found from dishwasher and refrigerators.
Other useful sources are Statistics Finland’s lists of wastes from production and consumption
that gives estimates for potential BFR applications, e.g. for year 1997: discarded electronic
equipment 411 tons from industry (excluding transformers and capacitors containing PCB or
29
PCT) and 3 tons from households. Undefined waste from electric and electronic industry 4
tons. [21]
5.2 Sweden
In 1998 the National Chemicals Inspectorate (KemI) was commissioned by the Government
to investigate how best to phase out the brominated flame retardants PBDE and PBB. On 15
March 1999, KemI submitted a proposal to prohibit the use of PBDE och PBB. PBDE is not
manufactured in Sweden but is imported and used in cables of rubber, for instance. The
largest amounts are contained in imported electronic components and included in, for
example, computers, tv-sets and cars. Before 1990, PBDE was also used in Swedish textiles.
Today, it may occur in imported textiles and upholstered furniture. Neither is PBB
manufactured in Sweden, but may be included in imported products containing electronics.
[22] In Table 11 the import of brominated flame retardants to Sweden is presented.
Table 11. Import of brominated flame retardant to Sweden in metric tons. [10]
Year 1993 1994 1995 1996 1997 1998
PBDE 22 90 20 79 123 41*
HBCD 50 80 90 83 125 89
TBBPA 488 450 258 291 303 269
* Only DeBDE – containing products were imported
The World Health Organisation (WHO) has called for PBDEs “not to be used where suitable
replacements are available” [6]. The PBDEs are currently moving slowly out of the EU's
existing chemicals processing, but Sweden is pushing towards a ban on PBBs and PBDEs
within 5 years. [10]
The Swedish Chemicals Inspectorate have produced a report on ”Phase-out of PBDEs and
PBBs”, available on the internet. [23]
5.3 Denmark
In Denmark a extensive report on BFRs has been made. The report was published in year
1999 and contains detailed mass and product flow analyses of BFR streams. Import, export
30
and production of brominated flame retardants as chemicals according to the trade statistics
from Statistics Denmark are shown in Table 12. The statistic data include the high volume
aromatic brominated flame retardants as PBDEs, TBBPA and TBBPA derivatives. The net
supply of these compounds in 1997 totals 29 tonnes. [4]
Vinylbromide is not included in table 11 as this compound in the statistics is registered under
the same commodity position as dibromoethane that is used in high quantities as gasoline
additive. [4]
derivatives of other cycloalkanes, -alkenes -terpenes”. The Danish import and export of these
chemicals was 0 tonnes in 1997. [4]
Other brominated flame retardants may be registered under commodity positions including
other halogenated compounds, but it is supposed that the compounds included in Table 12
represent the major part of the supply of brominated flame retardants. [4]
The chemicals are used for compounding in Denmark. According to information from
compounders it is estimated that most of the flame retardants used by compounders are
reexported with compounds and masterbatches.[4]
The net supply of bromine derivatives of aromatic ethers, including the PBDEs, has decreased
from about 20 tonnes per year in the period 1993-1995 to around 1 tonne in 1997 (Figure 9).
The decrease in the supply of PBDEs is in accordance with the general trend in the use of
these substances. [4]
To nn
es
Figure 9 Import of brominated flame retardants with plastic compounds and
masterbatches for production in Denmark 1997. (picture taken from [4])
Table 12. Import, export and production of brominated flame retardants
as chemicals according to the trade statistics from Statistics Denmark. [4]
Flame retardant Supply % of total
Supply Plastic
ABS, PET
Brominated polyetherpolyol
Other BFRs 1 ) 6 3.8 3.6 UPE, PA
Total (estimated) 130-190 100 57-81 Notes: 1 ) Includes brominated polystyrene and dibromopentyl glycol. 2 ) Bromine content is calculated assuming a bromine content of TBBPA and derivatives of 59%
(TBBPA) and of other BFRs of 60% (correspond to polybrominated polystyrene). 3 ) Decabromodiphenyl ether, DeBDE
32
5.4 EU
In contrast to the WHO and Sweden, the UK Department for Trade and Industry published a
report claiming that concerns about these chemicals were “chemical paranoia or
chemophobia”. [24] The EU is currently drawing up proposals that will ban the use of PBDEs
and PBBs in electrical equipment [22], these proposals are being fought by the American
Electronics Association [70]. The EU ecolable already excludes brominated flame retardants
and Dell Computers intend to comply [71]. Both NEC and Philips are working on replacing
BFRs [72, 73].
5.5. USA
The quantity of bromine sold or used in the United States according the Chemical Market
Report 1999b was 239 million kilograms and end uses are as follows: additives and oilfield
completion fluids, 20%; agricultural chemicals and fumigants, 22%; communications,
construction, electronics, textiles application and transportation 28% and halons,
pharmaceuticals, photography, rubber and water treatment, 30% in year 1998. The flame
retardants’ part of bromine primary use was 40%. [25]
5.6 Japan
Europe’s attitude towards halogen flame retardans has also affected the Japanese, because the
companies who produce flame retardant and electrical export goods to Europe are worried
about regulation changes which would cause a ban on halogen-based FRs. Table 13 gives
estimated amounts of flame retarted plastics in year 1997.
Table 13. Estimated amounts of flame retarted plastics in year 1997 in Japan [tons]. [26]
PS ABS PC/ABS PPE Total
Total
production
1 300 000 440 000 22 000 100 000 1 862 000
In flame
retarded plastics
92 000 83 000 22 000 100 000 297 000
% 7.1 18.9 100 100 16
33
Figure 10. Consumption of different flame retardants in plastics in Japan. (picture taken from [25])
In Japan’s market size of plastics as mentioned in Table 13, the rapidly growing amount
PC/ABS co-polymers is not shown. The demand of flame retarded plastics has been
increasing: bromine chemicals has the largest market share and phosphorous compounds,
inorganic materials and chlorine compounds follow. Bromine chemical consumption has
gradually decreased and phosphorous compounds consumption increased accordingly. Both
changes have been slight, however, as plotted in Figure 10.
5.7 BFR markets world wide
Brominated flame retardants are produced by a few manufacturers only. The world's major
BFR manufacturers are Great Lakes Chemical (USA), Albemarle Corporation (USA) and
Dead Sea Bromine Group (Israel). More than 70% of the market in the USA and Western
Europe is held by these companies. [4]
Because there isn’t yet legislation that demands register material volumes of brominated
flame retardants, most market analyses are assumptions based on market studies by
commercial companies such as Frost & Sullivan, country’s environmental authorities, or
34
statistics from manufacturers or coalition or forums of them, such as Bromine Science and
Environmental Forum (BSEF), Brominated Flame Retardant Industry Panel (BFRIP) and
European Flame Retardant Industry Panel (EBFRIP).
Table 14 lists major brominated flame retardants estimated market volume by region. Because
market volumes are estimates one can find conflicting amounts when comparing these
statistics to numbers given in Chapters 5.5 and 5.6. Still, however, markets are strongly
situated in high-tech Asian countries such as Taiwan and Japan. In Japan and the USA there
are much stricter fire safety regulations than in Europe and in Europe the demands for
replacing BFRs by non-halogen FRs have a much longer history than in United States and
Japan.
Deca-BDE (DBDPO) 24 300 7 500 23 000 54 800
Octa-BDE (OBDPO) 1 375 450 2 000 3 825
Penta-BDE (PBDPO) 8 290 210 -- 8 500
Total 58 655 30 860 114 800 204 325
Region’s market share 28.7% 15.1% 56.2%
35
6. Legislation
There are two types of legislation affecting the flame retardant industry, being fire regulations
and environmental regulations. Sometimes, these two are in conflict.
Flame retardants play an important role in protecting life and property. Interest groups, such
as the Alliance for Consumer Fire Safety in Europe (ACFSE) are well-organised and effective
in raising fire safety awareness. As a consequence, more stringent flammability standards are
being introduced. Different kinds of flammability tests are being standardised and products
have to pass strict fire safety tests and measurements before product sales are permitted. This
has resulted in a greater demand and changing requirements for flame retardants, favouring
low smoke and fume products.
Concern over the environmental impact of BFRs arose for the first time in 1973 when a
commercial flame retardant containing PBBs was accidently mixed into feed for dairy cattle,
livestock and poultry in the state of Michigan, USA. The feed was used widely, leading to
widespread PBB - contamination of milk, meat and eggs, and poisoning of animals. Over 9
million people were exposed to PBBs from food. Because of this widespread exposure, the
research was funded to improve the understanding of the toxicology of PBBs, and poisoned
animals and exposed humans have been studied as well. The effects of PBBs were found to be
essentially the same as those seen for PCBs.[10]
The most recent European Commission proposal for a directive on the restriction of the use of
certain hazardous substances in electrical and electronic equipment proposes the substition of
cadmium, lead, mercury and hexavalent chromium. The same applies for two types of
brominated flame retardants, being polybrominated biphenyl ethers (PBDE) and
polybrominated biphenyls (PBB) by 2008. [28]
Besides EU directives such as the proposal for the restriction of certain hazardous substancies
in electrical and electronic equipment [7] and World Health Organizations Health Criterias on
BFRs [6] there are several national regulations and guidelines concerning BFRs. Table 15
lists some prescribed legislation in industrialised countries.
36
Table 15. Survey of national activities concerning regulation, soft regulation,
risk and hazard assessment activities and national positions
on the issue of brominated flame retardants. [4]
Country Action – regulation Action - soft regulation Risk / hazard assessment
National position
Austria PBB and TRIS: manufacture, supply, import and use of compounds as chemical or preparation are banned 1)
Supports international regulation of PBDE and BFRs in general
Belgium No specific actions have been taken to ban certain uses of selected BFRs or to implement major measures to control, limit or reduce their risks (1994)
Awaits an international strategy
Denmark PBB s
2) and TRIS 2), 3) are banned in textiles, respectively textiles with skin contact
BFRs are on the Danish List of Undesirable Substances
The present substance flow analysis and assessment of alternatives 1998/99
Restrictions on these substances are desired because of their diffuse distribution in the marine environment
Finland PBB banned in textiles with skin contact 2)
Supports international restrictions on the use of BFRs
France PBB banned in textiles with skin contact 2)
Undertakes jointly with the UK risk assessment of OcBDE and DeBDE 4)
Germany Prohibitions on products contaminated with PBDDs/PBDFs
Regulation on producer/importer's responsibility at the waste stage
Voluntary substitution of halogenated compounds
An investigation of flame retardants at the German market is planned to be finished year 2000
PBB and PBDE must be banned
Japan Voluntary phase out of PBB, hexaBDE and tetraBDE
DeBDE is considered as a highly safe chemical
The Netherlands
Promulgation of regulation of PBB/PBDE was in 1994 on hold
Voluntary reduction of use of BFRs in end products
National risk assessments of PBB and PBDE in 1991 and 1994
There is a strong preference for international measures
37
National position
Sweden PBB and TRIS banned in textiles with possible skin contact 2)
The Swedish Government states that: PBB and PBDE will be phased out and the use of other BFRs should be limited Voluntary substitution in textile and telecommunication industries
Sweden has assigned HBCD for risk assessment in the EU 4)
Special attention is devoted to PBDE and PBB
Switzerland PBB and PBB containing products: manufacture, supply, import and use are banned
Advocate for a phase out of PBDE
United Kingdom
TRIS and PBB are banned in textiles with possible skin contact
2)
Undertakes jointly with France risk assessment of OcBDE and DeBDE. Has assigned PeBDE for risk assessment 4)
United States
Under way: Risk assessments of:
1. dioxin/furan contamination's in substances,
2. hazard potential of selected substances,
3. dioxins/furans from manufacture/com- bustion
1994: No national position on BFRs
Norway PBB and TRIS banned in textiles with possible skin contact 2)
The release of BFRs must be significantly reduced before the year 2010
An investigation of the domestic flow of BFRs is planned to be carried out in 1999
Italy Voluntary substitution of halogenated compounds through implementation of internal industrial standards 4)
1) Austrian ordinance BGB1.No.210/1993 2) Implementation of EC Dir. 76/769 3) Danish ordinance No 1042, §16/ 14-12-95 / 17-12-97. 4) Risk assessment of existing substances, regulation 793/93/EE 5) Examples are the following internal standards adopted by: ENEL – National Agency for Electric Energy
– and FS – National Railway – (CEI 20-37 standard); Milan City Underground (standard based on Sheet G 8998); and Marina Military (NAVI 3A075 standard). The achievement of these standards tends to exclude the use of halogenated flame retardants.
38
wastes containing BFRs. Attention focusses specially on waste management of electric and
electronic equipment basically for too reasons: WEEE streams include significant amounts of
precious metals such as copper, gold, silver and platinum and secondly these equipment are
the most important application of BFRs. European legislation is moving strongly toward
waste management systems addressing products that contain hazardous substances. There are
basically three ways to recycle products: to recycle the product itself, to recycle materials into
new products and to recycle the energy content of the product.
For many waste streams recycling routes may be blocked due to the presence of BFRs. For
example, the use of recycled ABS (acrylonitrile-butadiene-styrene) as a blend with PC
(polycarbonate) is not possible because the BFR causes the PC to depolymerise, resulting in
poor quality of the recyclate [30]. Feedstock recycling, i.e. the recovery of organic chemicals
or precious metals from waste streams that contain BFRs may partly be accomplished by
mechanical methods although it is recognised that, for example for WEEE, thermal methods
are generally more powerful [30]. Also, there is a large interest from the bromine industry to
recover bromine from waste streams that contain BFRs by means of thermal treatment [31-
32]. Most important examples here are DecaBDE found in HIPS (high impact polystyrene) in
brown goods and TBBPA used in ABS in data processing and office equipment as well as in
epoxy resins in printed circuit boards [32].
7.1 Mechanical recycling (of waste streams such as WEEE)
Mechanical processing and recycling of BFR-containing waste streams such as WEEE may
be accomplished by selective disassembly, shredding, magnetic and eddy current separation
as to so generate metal-rich fractions. The final stage produces an aluminium fraction and a
copper concentrate containing precious metals and combustible plastics [29]. A typical
mechanical recycling plant’s is based on a magnetic separator (iron, magnetic steel) and a
vibrating separator (for light fractions such as plastic and glass). For the rest of the metals
there is the possibility of manual sorting or different kinds of more specified and expensive
procedures such as eddy current separation for aluminium and flotation techniques, for
example for copper and zinc.
39
7.2.1 Contamination by BFRs and recovery / recycling
During recycling or recovery contamination presents itself in a many forms such as dirt,
partially oxidized polymers, printing inks, paper, pesticides, metals and additives such as
flame retardants. The potential for undesirable/antagonistic interactions and the probability of
undetected contamination being present, eventually leading to a reduction of the recyclate
quality, is high. [33]
Even if manufacturers could allow certain amount of impurities in recycled products another
problem lies with always changing additive characteristics and amounts. Basically the same
kinds of products could have completely different impurities now than 20 years ago. Of
course one may assume an average useful life of different consumer products such as
upholstered furniture, electronic and electrical products and so one. In addition to this, some
BFRs (most importantly PBB) have been banned due to potential toxic hazards recognised in
certain countries and it may be even legally impossible to recycle them. Contamination by
flame retardans is one of the most important factors that effect the recyclability of polymers.
The fate of bromine in thermal treatment has come more urgent through recent WEEE
recycling directive because it forces to recycle more WEEE than what is possible with
mechanical methods.
Thermal processing of the copper concentrate with high contest of precious metals, generated
by mechanical processing end-of-life electronic and electronic equipment (EEE), is currently
the most cost-effective and proven means to recover copper, precious metals and some energy
and at the same time achieve destruction of some hazardous substances. [29] The major
concern is the formation of brominated dioxins and furans but also HBr, Br2 and non aliphatic
compounds emissions must be investigated. There is a possibility to recycle flame retarded
polymers, “at least under certain experimental experimental conditions” according to Riess et
al. [34].
7.2.2 Recovery of bromine from bromine-containing wastes
It is also possible to recover bromine from WEEE in economically and ecologically feasible
way: the isolation of the bromine from the gas stream in a suitable form for reuse is based on
absorption into an aqueous (hydroxide) solution. The hydrogen bromide in the product gas
may be neutralised and converted into salt. Also a hydrobromic acid solution could be
produced as an end product. The bromine salts or residues are converted by the bromine
industry into bromine products, thereby closing the bromine loop. [31]
Upon incineration, combustion or gasification the bromine from brominated compounds will
distribute over bottom ash, fly ash and flue gas. Around 78% of the bromine was found in the
gas phase after combustion on a grate, while the other 20 % and 2 % were found in the fly ash
and grate ash, respectively [35]. Similarly, pyrolysis of two types of WEEE at 550°C
followed by gasification with oxygen at >1230°C [31] resulted in a bromine release of 20-98
% to the gas phase. Under these conditions the most important bromine compound is HBr,
with small amounts of Br2 and possibly metal bromides [31, 35-36]. The recovery of this is
accomplished either as HBr by adsorption in water (at pH=1) or by neutralisation with sodium
or calcium hydroxide, forming NaBr or CaBr2, where first process appears more feasible from
a bromine-recycling point of view [31,32,35].
These processes involve the risk of Br2 emissions from the scrubber that would need further
processing, whilst also the reaction Cl2 + 2HBr <=> 2HCl + Br2 may take place when large
amounts of chlorine are present, which shifts to the right-hand side with increasing
temperature. When also antimony (Sb) is present (as is always the case with PBDE-type
BFRs) SbBr3 may form, which will be oxidised or hydrolysed to Sb2O3 and HBr at lower
temperatures [35].
A recent study by the APME, Forschungszentrum Karlsruhe and EBFRIP [28,37] addressed
the options for WEEE co-firing in a municipal solid waste (MSW) combustor, at the same
time aiming at the recovery of bromine. The TAMARA facility at Karlsruhe was used. WEEE
fractions considered were shredded TV housings, shredded printed circuit boards and several
others. It was also here found that up to 90% of the bromine enters the gas phase, although 25
~ 40 % of the bromine from the TV set housings was found in the fly ashes. The HBr was
recovered from the flue gas using a scrubber operating at pH 1 or lower. Besides HBr, the
41
presence of Br2 was observed when the total bromine concentration gas phase was above
~300 mg/m3. This was found to correlate with SO2 concentration: the formation of Br2 is
followed by the oxidation of SO2 to SO3 via the reaction Br2 + SO2 + H2O <=> 2 HBr + SO3
[28], as illustrated by Figure 11.
The removal of Br2 from the flue gases is not straightforward but was accomplished by adding
Na2S2O3 to the second scrubber, which operates at pH around 7 (mainly for absorbing SO2).
Also it was found that the volatilisation of metals is increased by the presence of bromine,
similar to the effect of chlorine [49], resulting in increasing amounts of Cu, Zn, Sb and Pb in
the fly ash [37]. Altogether it was concluded that 2-3 %-wt WEEE containing ~2.5 %-wt
brominated flame retardants can be added to the MSW combustor feed, allowing at the same
time for the recovery of ~90% of the bromine. Preferably the bromine is recycled as a 48 %
HBr solution. Depending on the presence or availability of chlorine (to extract Br2 from
NaBr) on the site, the quality of the WEEE and market conditions for HBr, NaBr or Br2 the
most suitable route for recycling of bromine from WEEE are given in Figure 12 [37].
During pyrolysis of scrapped electronic circuit boards, it was reported by others that ~72 % of
the bromine was released to the gas phase, mainly as bromobenzene, C6H5Br, and HBr [14].
Several researchers working on the pyrolysis of BFRs or BFR-containing materials have
found no or only trace amounts of HBr in the product gases, finding methyl bromide (CH3Br),
ethyl bromide (C2H5Br) and propyl- and propylene bromide (C3H7Br and C3H5Br) instead
[15,38,39,44].
Figure 11 Speciation of bromine and sulphur in the gas phase during the TAMARA
tests (picture taken from [28])
42
7.3 Thermal treatment of bromine-containing wastes: processes
For the thermal treatment of waste streams that contain significant amounts of BFRs there are
basically as many behaviour paths as there are different BFRs because their chemical
properties are very different.
Basic thermal treatment methods are combustion or incineration, gasification and pyrolysis
from which the combustion is the most common. Grates or stokers, rotary kilns and
circulating fluidised beds (CFBs) are typical furnace types for thermal treatment for waste.
Rotary kilns are widely used to incinerate hazardous waste, grate furnaces are generally the
first choice for mass burning of municipal wastes. At the same time, CFBs are increasingly
being used for the co-firing of refuse derived fuels (RDF) usually with another fuel such as
coal, peat or biomass. All these methods are suitable for making use of the energy content of
organic part of waste, e.g., the plastics fraction in computer monitor housings. Recycling of
the energy content of an end-of-life product is also accepted in the EU’s latest WEEE
Figure 12 Options for bromine recovery from WEEE (picture taken from [37])
43
recycling directive [7] and after a thermal treatment the inorganic rest fractions are easier to
process with a mechanical recycling process.
7.3.1 Rotary kiln furnaces
A rotary kiln is very suitable for process where one option is material recovery. In an ideal
case, plastics and other organic compounds vaporise to the flue gases and for example
precious metals remain in ashes that are easily removed from the furnace. A basic working
scheme of a rotary kiln is given in Figure 13.
Figure 13. A Rotary Kiln.
Usually the working temperatures in kiln processes are above 1000°C but in metal recovery
processes temperature should be significantly lower because of the melting points of
recoverable metals. Because the most important metal in E+E waste is usually copper, the kiln
temperature shouldn’t rise above 700°C.
7.3.2 Mass burning on a grate
Mass burning on a grate, or stoker, is the most conventional way to accomplish waste
incineration. This system isn’t the best option for material recycling because the qualty input
varies much.
Pilot scale tests simulating conditions of typical MSW incineration plant were carried out at
Karlsruhe. The test’s input was combination of “typical” MSW besides a Br content of waste
was 100 times higher than usual. Addition of Br didn’t have negative influence upon the
44
combustion performance and 60-80% of the input’s Br inventory was released into the raw
gas. [16] (see also section 7.2.2)
7.3.3 Fluidised bed reactors
There are two basic types of fludized-bed furnaces, circulating and bubling. Basic idea in both
is the same: lower parts of furnace are filled with solid particles which are set into motion (=
fluidization) by blowing a gas stream upward through the bed. Under the influence of the gas
stream the bed acts like boiling liquid. The bed’s mass is significantly higher than the fuel’s
mass which offers the possibility to feed in fuels with varying moisture and heat value
content. The bubbling bed mixes fuel well and heat transfer between fuels solid and gaseous
phases and bed’s solid particles and furnace walls is good. Figure 14 presents a circulating
fluidized bed plant, which is designed for the combustion of recovered fuels.
FURNACE
Figure14 CFBC-plant at Högdalen, Sweden. (picture taken from [40])
Because the halogen (typically chlorine) content of fuel the inner heat transfer surfaces are
located after flue gas cooling channel and in the solids return in order to avoid high
temperature corrosion.
7.3.4 Pyrolysis drums and other pyrolysis systems
There are several different kind of pyrolysis systems designed for thermal treatment of waste.
Some of those apllications have are already in full scale plant size and they are in commercial
use. One of those systems is the Japanese R21 system (see Figure 15) which can handle even
150 000 tonnes of MSW per annum (depending on plant size).
Benefits of this kind of system, from a material recycling point of view, are that because the
furnace is drum- like the residue doesn’t agglomerate and block furnace so easily as in other
types of furnaces and metals don’t oxidise because of the lack of air. The drum is heated
outside with heat coming from high temperature combustion chamber and the temperature
inside the drum is about 400°C. After organic fractions have been vaporised in the drum and
flue gases lead to high temperature combustion chamber and burned. Organic residue is
separated from inorganic and fed also to a high temperature combustion chamber. Because the
reducing conditions in pyrolysis drum and later high temperature burning of pyrolys gas, the
amount of PCDD/F compounds (and probably also PBDD/F compounds) are very low.
Figure 15. R21 Pyrolysis process. (picture taken from [41])
46
There are various other possibilities for pyrolysis reactors such as basic gasifier type of
solution where the gasifier is externally heated without oxidising conditions inside the reactor.
In this kind of system inorganic fractions can block inside the reactor. A possible pyrolysis
reactor is a bubbling fluidized bed in which the fluidizing gas is nitrogen. One of the
variations of this kind of system is studied (primarily for the combustion of high-PVC solid
waste with HCl recovery) at the laboratory of Energy Engineering and Environmental
Protection at Helsinki University of Technology [42, 44].
7.4 Formation of Brominated Dioxins and Furans During Thermal Processing of BFR- containing Wastes
Besides the possible environmental and health hazards caused by certain BFRs during their
production, their use in processes and or product life, a major point of concern is that
polybrominated – p- dibenzodioxids and dibenzofurans (referred to as PBDD/Fs) are formed
during thermal processes such as waste incineration. Indeed, brominated dioxins and furans
(PBDD/Fs) can be formed according to chemical routes similar to their chlorinated PCDD/F
analogues: also here the de novo formation route during cool-down of gases is important [43].
Very little is known about the toxicity of PBDD/Fs [24] although the WHO reports it to be
“more or less similar” to the corresponding PCDD/Fs [45]. Also, in many cases the PBDD/Fs
are accompanied by halogenated polyaromatic hydrocarbons (PAHs) that pose a greater risk
[24]. One aspect that must not be forgotten is that many chemicals like bromophenols and
BFRs such as PBDE and TBBPA are contaminated by small amounts of PBDD/Fs during
their production [45]. It is therefore not suprising that often the amount of PBDD/Fs formed
during thermal processing of BFR-containing materials is smaller than the amount that is
destroyed, i.e. the process acts as a sink for PBDD/Fs [43, 46].
When compared to the “more common” PCDD/Fs the PBDD/Fs are characterised by higher
molar masses, lower melting points, lower vapor pressures and lower water solubilities. One
important difference is the high sensitivity to photolysis, i.e. destruction (bromine removal)
under the influence of light: lifetimes for PBDD/Fs may vary from less than one minute in the
47
atmosphere to several months in soils. PBDD/Fs are generally found in the atmosphere bound
to particles. As with PCDD/Fs, the formation of PBDD/Fs during thermal treatment of BFR
containing polymers is depending on oxygen, polymer types, temperature and additives such
as Sb2O3. The latter may bring down the temperature window where PBDD/Fs are formed
from typically 600-900°C to as low as 400°C. When also chlorine is present, mixed halogen
congeners ClxBryDD/Fs, also referred to as PXDD/Fs (X=F,Cl or Br) may be formed [45].
Sakai et al. [43] reported that the presence of metals such as Fe and Cu promotes the
formation of PBDD/Fs, whilst the ratio of PBDDs to PBDFs decreased with increasing
chlorine concentration.
For flame retardants such as polybrominated diphenylethers (PBDE) the chemical routes to
PBDD/Fs are very short, as seen in Figure 16 [47]. Zelinski et al. reported measured
concentrations of ~ 15 ppmw in deposits near a burned-out TV set after a residential fire [48].
Adding approx. 5 %-wt of PentaBDE to a municipal solid waste burnt in a German
incinerator yielded concentrations of 0.4-0.6 mg Br/kg as PBDD/F in fly ash removed by the
electrofilter [24].
Experiments made during the mid 1980s showed that up to 10% of the bromine from PBDEs
can form PBDD/Fs when heated to 510-630°C [51]. Somewhat later similar results were
presented for the range 600-800ºC, with the tetra- and penta-bromo substituted compounds as
the most “abundant” homologues, whilst for the other BFRs much smaller amounts of
PBDD/Fs were found after pyrolysis of polymers containing these compounds [52].
Figure 16. Formation of PBDD/Fs from PBDE flame retardants x+y=5,8, or 10 (picture taken from [47]).
48
The risks for PBDD/F formation is one reason why PBDE and PBB-type flame retardants are
more and more replaced by TBBPA or non-halogen flame retardants. As mentioned above,
Riess et al. [34] recently reported that PBDE are still found in polymers from electrotechnical
applications. Also very recently Wichmann et al. [50] analysed the formation of PBDD/Fs
from TBBPA in air at 600°C and found that amounts formed were not large (of the order of
20 mg PBDD/Fs /kg TBBPA) but not zero.
For lower temperatures, Hamm et al. [64] recently grounded and injection-molded
(temperatures up to 600 K) a HIPS polymer containing DeBDE and Sb2O3 repeatedly (5
times) as to simulate sequential recycling. Not more than 5 ppb total for the eight regulated
PBDD/F congeners was found.
As for the mixed brominated/chlorinated PXDD/Fs: recent work in Sweden on MSW samples
with BFRs in a fluidised bed combustor (FBC), showed for the three BFRs TBBPA, DeBDE
and HBCD, that CO emission levels in the flue gas were increased while SO2 levels decreased
with BRFs present in the fuel [61]. This corresponds to findings at Karlsruhe, showing that
SO2 is oxidised to SO3 (see Chapter 7.2.2). At the same time, PCDD/F concentrations
decreased somewhat, although tetra-BDD/Fs were found, which were formed apparently
along the same routes as the tetra-CDD/Fs. Most abundant, though, were the mixed
ClxBryDD/Fs, showing for their relative amounts a Gaussian distribution from (x=4, y=0) i.e.
tetra-CDD/F, to (x=0, y=4) i.e. tetraBDD/F, peaking at (x=2, y=2), i.e. dichlorodibromo
DD/Fs. No BFRs were found in the flue gas. It was suggested that the species BrCl is present
in the gas in significant amounts at temperatures up to 700ºC, which affects the PCDD/F
formation via the reaction Br + Cl2 → BrCl + Cl [61].
Similarly, also in the US recent studies [62] showed that brominated organic species present
in the feed of a chlorinated waste incinerator may reduce PCDD/F emissions by as much as
30% at a Br/Cl molar ratio of 0.1 in the feed. In this case, despite experimental limitations
(lack of calibration standards!) three “larger” PXDFs were detected: Cl6BrDF, Cl5Br2DF and
Cl7BrDF. Another finding was that with bromine present, the presence of chlorobenzene in
the flue gas shifted to the presence of bromobenzene.
49
8. On-line and Off-line Analysis Techniques for Identification and Concentration Measurement of Brominated Chemicals in Waste Streams and Gases
For the detection and quantitative analysis of brominated chemical compounds in waste
streams and in the exhaust gases and solid residues from thermal treatment processes two
methods are the most important: mass spectroscopy (MS) and infrared analysis (IR). Besides
these, several wet-chemical and other methods are used as well. The analytical methods for
the characterisation are listed in Table 16 [34].
Table 16. Analytical methods for the characterisation of halogen and polymer samples.
Analytical method Purpose
with thermogravimetric methods
Energy dispersive x-ray fluorescence
mass spectrometric detection (HRGC/MS)
furans (PBDD/F)
8.1 Mass spectroscopy + gas chromatography (MS-GC)
The use of mass spectroscopy takes full benefit that the halogen compounds Cl and Br occur
in nature as two isotopes: Cl as 35Cl and 37Cl, at a ratio 3:1, and Br as 79Br and 81Br at a ratio
1:1. Thus, an ion containing one Br atom can be identified as a double peak at m/z
(mass/charge) = M and at M+2 in an MS spectrum, one containing two Br atoms as 3 peaks
with an intensity ratio 1:2.1 at m/z = M, M+2 and M+4, etc. [53]. For example, the MS
spectrum of CH3Br shows peaks at m/z = 15 (CH3), 79 (79Br), 81 (81Br), 94 (CH3 79Br) and 96
(CH3 81Br). This is illustrated by the spectrea given in Figure 17, for brominated compounds
which have been measured in ambient air [55].
50
A clear disadvantage of the method is the high cost and the fact that fragments of the orginal
compound are detected which can make species identification difficult. Nonetheless, a lot of
research on polymer thermal degradation, including BFRs is based on pyrolysis+gas
chromatography/MS (Py-GC/MS) [14, 34, 38, 39, 51, 54]. High-resolution MS methods (GC-
HRMS) can be optimised to detect brominated compounds in air at concentration below the
parts-per-trillion level. For example, methyl bromide (CH3Br) was detected at around 15 ppt
in ambient air the US during Fall 1998 [55].
Figure 17 Examples of mass spectra of brominated species that have been detected in
air samples (picture taken from [55])
51
According to Wang [56] the combination GC + atomic emission detection, i.e., Py-GC/AED
has advantages over Py-GC/MS because for BFR compounds, for example, “there is no good
way to know the identity of the aliphatic or aromatic counterpart to which the halogen
element is attached”. The procedure applies the emission lines of carbon, hydrogen and
bromine at 496, 486 and 478 nm, respectively. A specific polymeric flame retardant for
example can be identified by a peak pattern after a sufficient set of calibrations is made. The
analysis of a BFR within a polymer matrix are preferred over the analysis of a pure BFR.
With respect to the gas chromatograph (GC) that is used upstream of the MS analyser: in
order to separate the compounds present in a mixture, standard data are a typical problem
when dealing with compounds related to brominated flame retardants. This especially holds
for the brominated dioxins and furanes, PBDD/Fs, not to mention the mixed ClxBryDD/Fs, for
which 5020 congeners are possible. Recently correlations were reported that relate the GC
retention time of PBDDs to that of the analogue PCDDs. When expressing the retention time
by a capacity factor, k, as a function of temperature, T, via ln k = A + B/T, it was reported by
Liang et al. [65] that the parameters for PBDDs and PCDDs are correlated by the simple
relations APBDD= 0.506 + 1.063APCDD and BPBDD= -2469.1 + 1.427BPCDD, with regression
coefficients R2 > 0.99. This should hold for all 75 PBDD congeners. GC column temperatures
used were in the range 200 - 270ºC [65].
8.2 Infrared (IR) spectroscopy
Infrared spectroscopy is based on the absorption of infrared light at frequencies specific for
stretching, bending and other oscillations inside molecules. Typically the frequency range
from 2.5 to 25 micrometer, or wavenumber 400 – 4000 cm-1 is used, although lower
wavenumbers (far infrared frequencies) may also be used. Nowadays the method is always
combined with Fourier transform-based signal processing procedures, referred to as FT-IR
[53]. For BFRs, important frequencies are approx. 2555 cm-1 for HBr, 755 cm-1 for
bromobenzene, approx. 3000 cm-1 and approx. 1500 cm-1 for methyl benzene, approx. 3100
cm-1 and approx. 1500 cm-1 for benzene. Also important are the frequencies for water (1300-
1900 cm-1 and 3500-4000 cm-1) and carbon dioxide (2300-2400 cm-1) [14,57]. As an
illustration, the FT-IR spectrum of HBr, measured as part of the research at the lab for Energy
Engineering and Environmental Protection [15,44] is given in Figure 18. One benefit of this
technique is that it is nowadays available at reasonable cost, although calibration work for
52
“non-conventional” species such as HBr and CH3Br requires standardised samples that may
be hard to find. Also, many halogenated compounds have their “fingerprint” frequencies at
low wavenumbers, i.e. below 800 cm-1.
Figure 18 FT-IR spectrum for HBr (from 100 ppm HBr in N2 mixture)
8.3 Other methods
Measurement of nuclear quadrupole moment of 81Br has been used successfully to detect
how brominated flame retardants are dispersed in a polymer matrix, and to determine the
crystal structure of brominated aromatic compounds. Using an NMR (nuclear magnetic
resonance) spectrometer (10-300 MHz) spectral signals were obtained in the range 227 – 256
MHz with at accuracy of the order of 1 MHz. [58, 59]. This method is based on the fact that
the nuclei of atoms such as 1H, 13C, 19F and apparently also 81Br have a spin that gives rise to
magnetic field that can be measured [53]. Similar to mass spectroscopy methods, this method
is quite expensive and especially in this case requires highly skilled personnel. Fraunholcz and van Kooy [66] very recently suggested to use X-ray transmission, similar as is
being used to scan luggage at airports, for detecting heavy elements such as chlorine, bromine
or heavy metals. After this, selected particles can be separated and submitted to more detailed
analysis. When using a dual energy method (as modern airport scanners use) the elements
detected can be further separated into several classes.
53
9. Summarising conclusions
Brominated flame retardants BFRs are effective at increasing fire safety of several products,
mainly textiles and polymers that are used in electrical and electronic (E+E) equipment. The
production of BFRs and BFR-containing products and the fact that most of these products end
up in waste streams after only a few years resulted in measurable quantities of BFRs in the
environment rather soon after their large-scale introduction into the market. This resulted in
many sometimes very extensive studies (e.g. [4]) as to the effects of BFRs on the indoor and
outdoor environment, followed by studies addressing the processing of BFR-containing end-
of-life products (like the present report) and, most recently, the recovery of bromine in
combination with BFR-containing waste processing [37]. Against a current BFR consumption
in Europe of 3000 – 35000 tonnes/year, approximately 8000 tonnes of bromine may be
recovered and recycled from WEEE.
After a worldwide phase-out of polybrominated biphenyls (PBBs), the polybrominated
diphenyl ethers (PBDEs) are, at least in Europe, being more and more being replaced by the
most important BFR nowaydays: tetrabromo bisphenol A (TBBPA). The PBDE penta-BDE is
to be phased out before the end of 2003 while EU risk assessments are ongoing for octa- and
deca-BDE, as for TBBPA as well. At this point differences are arising between Europe and
USA + Japan, where fire regulations are more tight. This will result in lower consumption or
phase out of BFRs in Europe that will be widely used elsewhere, and could interfere with
future international trade of BFR containing products, most importantly consumer electronics.
One potential environmental and human health hazard is formed by polybrominated dioxins
and furans, in short PBDD/Fs, i.e. the brominated analogues of chlorine-containing,
supertoxic PCDD/Fs. Not only are these present in very small amounts in BFRs and BFR-
containing products, they may also be formed during the incineration, combustion, pyrolysis
or other type of thermal processing of BFR-containing waste, by ways rather similar to the
chlorinated dioxins/furans. Especially the abovementioned PBDEs show a great tendency to
form PBDD/Fs. The picture is made more complex by the mixed chlorinated/brominated
dioxins, for which 5020 congeners exist. This issue will and should receive a lot of attention
still in the years to come.
54
BFRs do affect thermal processes for waste treatment, but at the typical temperatures at which
BFR-containing wastes are thermally treated (typically 500-1000°C) they will be destroyed
and converted mainly to HBr and Br2, although also other species may be formed. Similar to
flue gas scrubbing for HCl this can be done as well for HBr, a recyclable by-product.
Depending on e.g. the amount of sulphur, water and oxygen present, Br2 may be formed as
well which requires an additional flue gas scrubber. In principle any type of process that
allows for the thermal treatment of waste may be used for BFR-containing waste streams. For
example, also a ”newer”, less conventional waste (from an incineration point of view) such a
sewage sludge from waste-water treatment was found to contain BFRs [63]. The work with
the TAMARA facility in Karlsruhe suggests that a few percent of BFR-containing material
can be co-fired in a municipal solid waste incinerator, allowing for recovery of the bromine
[37].
Two aspects that have not received sufficient attention must still be mentioned at this point:
• HBr is very corrosive in a wet environment. In the scarce literature on this it was reported
that while ASTM 316-type steel can resist dry HBr when tested up to 450°C, but that
nickel or Hastelloy metal is to be used when the amount of water in the gas is more than 1
ppmv [67],
• Methyl bromide (bromoform, CH3Br) is listed as an ozone depleting gas [60] which
could mean that its emissions may have to be monitored in the future as part of recent EU
directives [68]
[2] http://www.flameretardants-online.com/german/fsm_systeme/index_fsm_systeme.htm
[3] Lyons, John W. The Chemistry and Uses of Fire Retardants, Wiley-Interscience, John Wiley, New York 1970.
[4] Lassen, C. L∅kke, S. Hansen, L. Brominated Flame Retardants- Substance Flow Analys and Substitution Feasability Study. Ministry of Miljoproject nr. 494, Kobenhagen 1999
[5] Dead Sea Bromine Group product information, www.dsbgfr.com, online 20.3.2002
[6] WHO, Brominated diphenyl ethers, Enviromental Health Criteria 162, 1994
[7] Proposal for a directive COM (2000) 347 – C5-0415/2000 – 2000/0159(COD)
[8] EBFRIP, Review of the explanatory memorandum to the European Comission proposals
on waste electrical and electronic equipment, 31.10.2000
[9] Per Hedemalm, Per Carlsson, Viveca Palm, Waste from electrical and electronic products- a survey of the contents materials and hazardous substances in electric and electronic products. TemaNord 1995:554. Nordic Council of Ministers. Copenhagen 1995. 96.
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[11] US consumer product safety commission, Flame Retardant Chemicals That May Be Suitable for Use in Upholstered Furniture, memorium of pubic hearing, 1998 http://www.cpsc.gov/businfo/frnotices/fr98/retardant.html, online 11.11.2002
[12] Toxicological Risks of Selected Flame-Retardant Chemicals, Subcommittee on Flame- Retardant Chemicals, Committee on Toxicology, Board on Environmental Studies and Toxicology, National Research Council, US 2000, 534p. Open book http://www.nap.edu/catalog/9841.html, online 10.10.2001
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[14] Chien, Y.-C., Wang, H.P., Lin, K.-S., Huang, Y.-J., Yang, Y.W. (2000) “Fate of bromine in pyrolysis of printed circuit board wastes” Chemosphere 40, 383-387
[15] Tohka, A., Zevenhoven R. , Brominated Flame Retardants- a nuicance in thermal waste processing?, manuscript accepted for an oral presentation TMS Fall 2002 Extraction and Processing Division Meeting on Recycling and Waste Treatment in Mineral and Metal Processing: Technical and Economical Aspects, 16-20 June 2002, Luleå, Sweden.
[16] Vehlow, J., Bergfeldt, B., Jay, K., Seifert, H., Wanke, T. Mark, F.E, Thermal Treatment of E+E Waste Plastics. Waste Management and Research, 18, 131, 2000.
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[19] Nurmi, V., Sääskilahti V., Törmänen M., Hietaniemi J., Mangs, J., Hakkaraien T., Sähkölaitteiden palo-ominaisuudet ja sähkölaitepalojen sammuttamien – kokee